摘要:

AbstractCortical connections of the dorsomedial visual area (DM) of owl monkeys were revealed with injections of the bidirectional tracer, wheatgerm agglutinin conjugated with horseradish peroxidase (WGA‐HRP), or the retrograde fluorescent tracer, diamidino yellow. Microelectrode recordings in two cases identified DM as a systematic representation of the visual hemifield in a densely myelinated rectangle of cortex just rostral to the dorsomedial portion of the second visual area (V–II, or area 18). Cortex was flattened and cut parallel to the surface in all cases so that the myeloarchitectonic borders of DM and other areas such as the primary visual area (V‐I or area 17), V‐II or area 18, and the middle temporal visual area (MT) could be readily determined, and the surface view patterns of connections could be directly appreciated. The ipsilateral pattern of connections of DM were dense and visuotopically congruent with area 17, area 18, and MT, and moderate to dense connections were with the medial visual area (M), the rostral division of the dorsolateral visual area, the dorsointermediate area, the ventral posterior area, the caudal division of inferotemporal cortex (ITc), the ventral posterior parietal area, and visuomotor cortex of the frontal lobe. The connections of DM were concentrated in the cytochrome oxidase (CO)‐dense blobs of area 17, the CO‐dense bands of area 18, and the CO‐dense regions of MT. Callosal connections of DM were with matched locations in DM in the opposite hemisphere, and with VPP.The ipsilateral connections of DM with area 17 were confirmed by injecting WGA‐HRP into area 17 in one owl monkey. In addition to labelled cells and terminals in area 18 and MT, bidirectionally transported tracer was also apparent in DM. Evidence for the existence of DM in other primates was obtained by injecting area 17 and examining the areal patterns of connections and myeloarchitecture in three species of Old World monkeys, two additional species of New World monkeys, and prosimian galagos. In all of these primates, one of three major targets of area 17 was a densely myelinated zone of cortex just rostral to dorsomedial area 18, in the location of DM in owl monkeys. Thus, it seems likely that DM is a visual area common to all primates. © 1993

ISSN:0092-7317    

DOI:10.1002/cne.903340402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe development of retinal ganglion cells (RGC) was studied in the chick from stage 18 to adulthood. Our main objectives were to identify the retinal site where the first RGCs differentiate, to locate this site relative to the optically defined central retinal area, and to map the spatial arrangement of the RGC field at different stages in development. The eyes of the experimental animals were fixed and serially sectioned. The borders of RGC fields were determined from the presence of either ganglion cell perikarya or ganglion cell axons. In seven cases between stages 21 and 26, the borders of the RGC fields were confirmed electron microscopically. The serial sections together with the RGC fields were then reconstructed in three dimensions. The reconstructed retinae were projected onto a plane by using the radially equidistant polar azimuthal projection.First, RGCs appear dorsal to the apex of the optic fissure. Ganglion cell development then initially spreads out symmetrically with respect to the optic fissure. However, from stage 29 on, the nasal half of the retina expands much more than the temporal half. This asymmetrical growth entails that the optic fissure is eventually located in the temporal half of the retina in the mature animal.The RGC fields of the embryonic stages were superimposed on the retina of a visually active animal according to their real size and position. It turned out that the central retinal area was at least 2 mm away from the site where the first RGCs were generated. It is not before stage 28 that the prospective central retinal area is included into the expanding ganglion cell field. The fact that RGCs at the central retinal area are generated 2.5 days later than first RGCs near the apex of the optic fissure has important implications for the formation of the retinotectal projection. © 1993 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903340403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA wide variety of retinal pathology is associated with an increase in Müller glial cell expression of glial fibrillary acidic protein (GFAP). In this study the time course and spatial spread of the Müller cell GFAP response following argon laser photocoagulation lesions was examined in wholemounted rabbit retina.At 24 hours single focal lesions were surrounded by GFAP positive Müller cell end feet which declined in density with distance but extended as far as 2–3 mm from the lesion. The Müller cell reaction reached a maximal spread of 4–5 mm at 14 to 21 days and had started to contract by 30 days, leaving a core of GFAP positive processes immediately around the lesion site at 60 days. This zone of spread was much larger than the area of disrupted pigment epithelium. Isodensity plots did not reveal any correlation with the trajectory of retinal ganglion cell axons. The spread of reaction was more confined for lesions within the visual streak than in the dorsal or ventral retinal periphery.Multiple lesions within a focal region of retina resulted in a greater density of GFAP reactive end feet with a corresponding greater spread. However, when five to ten lesions were made in a horizontal row, the Müller cells over the entire retina became GFAP immunoreactive. This pan‐retinal reaction took several days to spread, peaked at 7–14 days, and contracted back to the primary lesion sites by 2 months.This spread of Müller cell reactivity may be triggered by the diffusion of substances released by injury or it may be due to direct cellular communication. The extensive indirect effect on Müller cells of laser irradiation might be an important component of the clinical effect of laser photocoagulation and indicates a long distance communication mechanism between retinal glia which is poorly understood. This study also shows the importance of the time at which the Müller cell response is assessed. © 1993

ISSN:0092-7317    

DOI:10.1002/cne.903340404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractPrevious studies have found that the volume of several song control nuclei is larger in male songbirds than in female songbirds. The degree of this volumetric sex difference within a given species appears to be systematically related to the degree of the behavioral sex difference. The largest volumetric differences have been reported in species in which the male sings and the female sings little, if at all, and the smallest sex differences in volume have been reported in species in which males and females both sing in nearly equal amounts. We compared the volume of three song control nuclei in male and female European starlings (Sturnus vulgaris), a species in which females are known to sing, though at a much lower rate than males. We investigated the volume of hyperstriatum ventrale, pars caudale, nucleus robustus archistriatalis, and area X of the lobus parolfactorius as defined with the use of a Nissl stain. In addition, we measured the volume of area X as defined by the density of muscarinic cholinergic receptors visualized by in vitro receptor autoradiographic methods. The volumes of all three of the song nuclei, as defined by Nissl staining, are significantly larger in males than in females. For area X, Nissl staining and receptor autoradiography indicate the same significant volumetric sex difference. The three nuclei are approximately one and one half to two times larger in males than in females, a degree of dimorphism that is intermediate to those reported for other species. Previous investigations of sex differences in the avian vocal control system have used only Nissl stains to define nuclear volumes. We demonstrate in this paper that receptor autoradiography can be used to assess dimorphisms in nuclear volume. Broad application of this approach to a number of neurotransmitter receptor systems will better characterize the dimorphisms in the song system, and therefore will provide greater insight into the neuroanatomical and neurochemical control of birdsong. © 1993 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903340405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractIn rodents, the facilitation of sexual receptivity by estradiol and progesterone is suspected to be mediated by a network of neurons containing estrogen and progestin receptors. In female guinea pigs, this network would include estrogen receptor‐immunoreactive (ER‐ir) neurons located within the rostro‐ventral ventrolateral hypothalamus (r‐vVLH). This hypothesis predicts that a proportion of the neurons projecting to the r‐vVLH contains estrogen receptors. This prediction was tested through retrograde tracing combined with immunocytochemistry for estrogen receptors. Retrogradely labelled neurons were particularly abundant within the medial preoptic nucleus (MPN), bed nucleus of the stria terminalis (BST), anterior hypothalamus, amygdala, and lateral parabrachial nucleus. As predicted by the hypothesis, retrogradely labelled neurons were mostly observed in estrogen receptor‐rich areas. Retrogradely labelled neurons also containing estrogen receptor‐immunoreactivity (ER‐IR) were primarily found within the MPN, BST, and amygdala. However, a majority of retrogradely labelled neurons did not contain ER‐IR. As the preoptic area and the r‐vVLH are both responsive to estradiol in the facilitation of sexual receptivity by progesterone, these data are consistent with the hypothesis tested. However, our data also suggest that the network of neurons controlling sexual receptivity may include elements not directly sensitive to estradiol. Finally, the location of retrogradely labelled neurons is discussed with respect to the stimuli provided to the r‐vVLH in the context of sexual receptivity facilitated by estradiol and progesterone.

ISSN:0092-7317    

DOI:10.1002/cne.903340406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractProsaposin is the precursor for saposins A, B, C, and D, which are small lysosomal proteins required for the hydrolysis of sphingolipids by specific lysosomal hydrolases. With a monospecific anti‐saposin C antibody, which cross‐reacts with prosaposin but not with saposin A, B, or D, the present immunoblot experiments showed that the rat brain expresses an unprocessed ∼ 72 kDa protein (possibly prosaposin) and little saposin C. Regional analysis demonstrated that prosaposin is abundant in the brainstem, hypothalamus, cerebellum, striatum, and hippocampus, and less abundant in the cerebral cortex. Consistent with this finding, prosaposin‐like immunoreactive neurons and fibers as revealed by immunohistochemistry were observed frequently in subcortical regions. The medial septum, diagonal bands, basal nucleus of Meynert, ventral striatum, medial habenular nucleus, and motor nuclei of cranial nerve had significant numbers of immunoreactive neurons. There were also nerve fibers with prosaposin‐like immunoreactivity in several projection fields of the above nuclei. Other brain areas that contained prosaposin‐like immunoreactive neurons and/or processes were: several brain nuclei (nucleus caudate putamen, globus pallidus, substantia nigra, red nucleus) constituting the so‐called extrapyramidal system, reticular thalamic nucleus, entopeduncular nucleus, mammillary nuclei, auditory relay nuclei, cerebellum, sensory cranial nerve nuclei, and the reticular formation. The distribution pattern of prosaposin is apparently different from that of other neuroactive substances so far examined, and thus prosaposin may be involved in novel central events. © 1993 W

ISSN:0092-7317    

DOI:10.1002/cne.903340407

出版商:Wiley‐Liss, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe nucleus accumbens is composed of a core region involved in motor functions and a shell region implicated in emotional and motivational processes. Both of these regions receive serotonin‐ and dopamine‐containing afferents. We examined whether the serotonin innervation or relation to catecholamine (mainly dopamine) axons in the nucleus accumbens shows common features or specializations corresponding to the noted functional differences in core and shell subregions. To address this question, we examined the ultrastructure of serotonin‐containing axons and their relation to catecholamine‐containing afferents in either the core or shell of the nucleus accumbens. Single coronal sections through the rat forebrain were processed for immunoperoxidase labeling of serotonin and immunogold silver labeling of tyrosine hydroxylase, the catecholamine‐synthesizing enzyme. Varicose processes showing peroxidase product for serotonin by light microscopy were confirmed to be axons and terminals by electron microscopy. In a quantitative analysis of serotonin‐immunoreactive terminals forming one or more contacts in single sections, some common features were observed. For the core (n = 120) and the shell (n = 82), 41% formed synaptic junctions with unlabeled dendrites, 75% were in apposition with unlabeled terminals, which often formed asymmetric junctions, and 20% were in apposition with axons or terminals containing tyrosine hydroxylase. Thus, in both the core and shell of the nucleus accumbens, serotonin terminals synapse on postsynaptic neurons and are likely to modulate or be modulated by presynaptic interactions with excitatory axons forming asymmetric junctions and by catecholaminergic afferents.Marked differences in the morphology of serotonin axons were also seen in the core versus shell of the nucleus accumbens. By light microscopy, serotonin‐immunoreactive axons were thicker and more varicose than those found in the core. Ultrastructural analysis confirmed that, in contrast to the core, serotonin‐immunoreactive axons and terminals in the shell were larger in cross‐sectional diameter size (0.7 μm vs. 0.3 μm). Additionally, serotonin axon terminals in the shell contained more numerous immunoreactive large dense core vesicles and more frequently formed symmetric as opposed to asymmetric contacts with dendrites. The larger size and more numerous dense core vesicles in serotonin‐immunoreactive terminals in the shell support the concept that serotonin or co‐existing neurotransmitter may be more tonically released in the shell versus core of the nucleus accumbens.

ISSN:0092-7317    

DOI:10.1002/cne.903340408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have recently shown in cats that many neurons projecting to the lateral geniculate nucleus from the pretectum use γ‐amino butyric acid (GABA) as their neurotransmitter. We sought to determine the morphology of synaptic terminals and synapses formed by these pretectal axons and the extent to which they resemble other GABAergic terminals found in the geniculate neuropil (i.e., from geniculate interneurons and cells of the nearby perigeniculate nucleus). To do this, we labeled a population of pretectal axons with the anterograde tracerPhaseolus vulgarisleucoagglutinin and analyzed the morphology and synaptology of labeled pretectal terminals in the A laminae of the cat's lateral geniculate nucleus. The pretectal projection, which arises primarily from the nucleus of the optic tract (NOT), provides synaptic innervation to elements in the geniculate neuropil. The labeled NOT terminals are densely packed with vesicles, contain dark mitochondria, and form symmetrical synaptic contacts. These are characteristics of the F1 type of terminal, and we know from other studies that GABAergic axon terminals from interneurons and perigeniculate cells also give rise to F1 terminals. We compared our population of NOT terminals with labeled perigeniculate and unlabeled F1 terminals selected from the geniculate neuropil and found that all three populations share many morphological characteristics. Both qualitative and quantitative assessments of the pretectal terminals suggest that these are a type of F1 terminal. Most pretectal terminals selectively form synapses onto geniculate profiles that contain irregularly distributed vesicles and dark mitochondria and that are postsynaptic to other types of terminals. These postsynaptic targets thus exhibit features of another class of inhibitory, GABAergic terminal known as F2 terminals, which are the specialized appendages of geniculate interneurons. Pretectal inputs, being GABAergic, may thus serve to inhibit local interneuronal outputs. Pretectal axons also innervate the perigeniculate nucleus, in which the only targets are the other main type of inhibitory, GABAergic neurons. These results suggest that the pretectum may facilitate retinal transmission through the lateral geniculate nucleus by providing inhibition to the local inhibitory cells: the interneurons and probably perigeniculate cells. This would serve to release geniculate relay cells from inhibition. © 1993 Wiley‐Liss

ISSN:0092-7317    

DOI:10.1002/cne.903340409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractVisual abilities decline during aging, and many of these declines are due to neural changes in the retina or brain. We have begun studies of the monkey visual system to investigate the location and nature of these changes as well as to answer general questions about the effects of aging on neural structure and function. We began with the dorsal lateral geniculate nucleus (LGN) because it is the main structure through which visual information passes on the way to cortex and because the parallel parvicellular and magnocellular pathways are most easily identified and studied in the LGN. In the present experiment, we determined the sizes, densities, and numbers of LGN neurons in young‐adult (5 to 12.5 years) and old (23 to 27.5 years) rhesus monkeys. The measures were corrected for tissue shrinkage, and stereological procedures were used that yield unbiased estimates.In young‐adult monkeys, neuron densities were lower in the magnocellular layers (about 14,000/mm3) than in the parvicellular layers (23,000/mm3). Neuron density increased about 28% from anterior to posterior in both types of layers. There was an average of approximately 1,267,000 neurons in the parvicellular layers and 148,000 neurons in the magnocellular layers; however, there was substantial variability (1.9‐fold) among five brains studied.Aging produced a statistically significant decrease in neuron density in both the magnocellular (29% average decrease) and parvicellular (41% average decrease) layers. However, there was no significant loss of neurons. Rather, the density decrease was due to a small (nonsignificant) decrease in the number of neurons combined with a small (nonsignificant) increase in LGN volume. The increase in LGN volume was due to a significant increase in neuron soma‐size and proportional increases in the volume of glial cells, blood vessels, and neuropil. These results, together with those of other studies, suggest that the effects of aging on the primate visual pathway from retina through striate cortex are relatively subtle. It is possible that the major neural changes occur more centrally. Alternatively, individual differences in the effects of aging may require much larger samples or prior screening to observe consistent changes. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903340410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903340401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY